<!DOCTYPE html>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
  .modal {
    bottom: 0;
    left: 0;
    right: 0;
    position: fixed;
  }

  .modal-dialog {
    position: relative;
    overflow: auto;
    max-height: 400px;
    transform: translateY(0);
  }

  .modal-content {
    background-color: purple;
    height: 300px;
  }

  .modal-footer {
    height: 100px;
    background-color: blue;
  }

  .additional-content {
    height: 100px;
    background-color: purple;
  }
</style>
<div class="modal">
  <div class="modal-dialog">
    <div class="modal-content"></div>
    <div class="modal-footer"></div>
    <div class="additional-content"></div>
  </div>
</div>
